Studies will be made in rabbits to determine the chemical structure of the cannabinoid molecule necessary to impart an effect on intraocular pressure. These drugs will be administered intravenously to negate any possible influence of absorption difficulties across membranes. Other investigations will be directed towards screening various compounds isolated from Cannabis sativa by initial water extraction. These water soluble derivatives will be tested initially for biological activity, viz. intraocular pressure fall, following intravenous injection at a standard dose of 0.2 mg per animal. Compounds providing a large response (i.e. greater than 50% fall in intraocular pressure) will have complete dose-response curve generated. Those compounds which are most efficacious in inducing a fall in intraocular pressure will be further tested in rhesus monkeys for activity when given intravenously. Some experiments will be made with intravitreal or intracameral injection since intraocular penetration of these compounds into the monkey eye is negligible. These studies will, therefore, identify possible clinically beneficial agents which reduce intraocular pressure.